copyright © 2005 pearson education, inc. publishing as benjamin cummings explain the process of...
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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Explain the process of aerobic cellular respiration.
• (Total 8 marks)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• glucose is broken down to pyruvate in the cytoplasm;with a small yield of ATP / net yield of 2 ATP;and NADH + H+ / NADH;aerobic respiration in the presence of oxygen;pyruvate converted to acetyl CoA;acetyl CoA enters Krebs cycle;Krebs cycle yields a small amount of ATP / one ATP per cycle;and FADH2 / FADH + H+ / NADH / NADH + H+ / reduced compounds / electron collecting molecules;these molecules pass electrons to electron transport chain;oxygen is final electron acceptor / water produced;electron transport chain linked to creation of an electrochemical gradient;electrochemical gradient / chemiosmosis powers creation of ATP;through ATPase;
• [8]
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Chapter 7Chapter 7Chapter 7Chapter 7
Photosynthesis: Photosynthesis:
Using Light to Make Using Light to Make FoodFood
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Photosynthesis is the process by which certain organisms use light energy
– To make sugar and oxygen gas from carbon dioxide and water
Lightenergy
PHOTOSYNTHESIS
6 CO2 6+ H2O
Carbon dioxide Water
C6H12O6 6+ O2
Glucose Oxygen gas
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• As the human demand for energy grows
– Fossil fuel supplies are dwindling
• Energy plantations
– Are being planted to serve as a renewable energy source
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AN OVERVIEW OF PHOTOSYNTHESIS
7.1 Autotrophs are the producers of the biosphere
• Plants are autotrophs
– Producing their own food and sustaining themselves without eating other organisms
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• Plants, algae, and some bacteria are photoautotrophs
– Producers of food consumed by virtually all organisms
Figure 7.1A–D
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7.2 Photosynthesis occurs in chloroplasts
• In plants, photosynthesis
– Occurs primarily in leaves, in chloroplasts, which contain stroma, and stacks of thylakoids called grana
Figure 7.2
Leaf Cross Section
Leaf
Mesophyll Cell
Mesophyll
VeinStoma
CO2O2
Chloroplast
Chloroplast
Grana Stroma
TE
M 9
,750
Stroma
Granum Thylakoid Thylakoidspace
OutermembraneInnermembrane
Intermembranespace
LM 2
,600
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7.3 Plants produce O2 gas by splitting water
• The O2 liberated by photosynthesis
– Is made from the oxygen in water
Reactants:
Products:
6 CO2 12 H2O
C6H12O6 6 H2O 6 O2
Labeled
Experiment 1
Experiment 2
6 CO2 12 H2O
6 CO2 12 H2O
C6H12O6 6 H2O 6 O2
Notlabeled
C6H12O6 6 H2O 6 O2
+
+
+
+
+
+
Figure 7.3A–C
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7.4 Photosynthesis is a redox process, as is cellular respiration
• In photosynthesis
– H2O is oxidized and CO2 is reduced
Figure 7.4A, B Reduction
Oxidation
6 O2 6 H2O
Reduction
Oxidation
6 O26 CO2 6 H2O C6H12O6
C6H12O6 6 CO2
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7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
• The complete process of photosynthesis consists of two linked sets of reactions
– The light reactions and the Calvin cycle
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• Light-dependent reactions
– Convert light energy to chemical energy and produce O2
• Light-independent (Calvin cycle) assembles sugar molecules from CO2
– Using ATP and NADPH from the light reactions
Figure 7.5
Light
CO2H2OChloroplast
LIGHTREACTIONS
(in thylakoids)
CALVINCYCLE
(in stroma)
NADP+
ADP+ P
ATP
NADPH
O Sugar
Electrons
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7.7 Photosystems capture solar power
• Thylakoid membranes contain multiple photosystems
– absorb light energy, which excites electrons
Figure 7.7A
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• Each photosystem consists of
– Light-harvesting complexes of pigments
– A reaction center with a primary electron acceptor that receives excited electrons from a reaction-center chlorophyll
Figure 7.7B, C
Ene
rgy
of e
lect
ron
Photon
Excited state
Heat
Photon(fluorescence)
Ground state
Chlorophyllmolecule
e–
Photosystem
Light-harvestingcomplexes
Reactioncenter
Primary electronacceptor
e–
To electrontransport chain
Pigment molecules
Chlorophyll a moleculeTransfer of energy
Photon
Thy
lako
id m
embr
ane
Online Lab: Chromatography
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7.8 In the light-dep. reactions, electron transport chains generate ATP and NADPH
• Two connected photosystems absorb photons of light
– transfer energy to chlorophyll P680 and P700
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• excited electrons
– passed from primary e- acceptor to electron transport chains
Figure 7.8A
Thylakoidspace
Photon
Stroma
Th
yla
koid
me
mb
ran
e
1
Photosystem II
e–
P680
2
H2O 12
+ 2O2 H+
3
ATPElectron transport chainProvides energy for synthesis of
by chemiosmosis
4
Photosystem I
Photon
P700
e–
5
+NADP+ H+ NADPH
6
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• Electrons shuttle from photosystem II to I
– Providing energy to make ATP
• Electrons from photosystem I
– Reduce NADP+ to NADPH
Figure 7.8B
e–
ATP
MillmakesATP
Pho
ton
Pho
ton
Photosystem II Photosystem I
NADPHe–
e–e–
e–
e–
e–
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• Photosystem II regains electrons by splitting water
– Releasing O2
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7.9 Chemiosmosis powers ATP synthesis in the light reactions
• The electron transport chain
– Pumps H+ into the thylakoid space from the stroma
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Chloroplast
Stroma (low H+ concentration)
Light Light
NADP+ + H+ NADPH
H+
H+
H+H+
ATPPADP +
Thylakoidmembrane
H2O 12
O2 2 H+ H+H+
H+ H+
H+
H+
H+ H+
H+
H+
Photosystem II Electrontransport chain
Photosystem I ATP synthase
Thylakoid space(high H+ concentration)
+
• diffusion of H+ back across the membrane through ATP synthase
– Powers phosphorylation of ADP to produce ATP (photophosphorylation)
Figure 7.9
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THE CALVIN CYCLE: CONVERTING CO2 TO SUGARS7.10 ATP and NADPH power sugar synthesis in the Calvin cycle
• Calvin cycle (Light-Independent Reactions)
– Occurs in the chloroplast’s stroma
– Consists of carbon fixation, reduction, release of G3P, and regeneration of RuBP
Figure 7.10A
InputCO2
ATPNADPH
CALVINCYCLE
G3POutput:
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• Using carbon from CO2, electrons from NADPH, and energy from ATP
– The cycle constructs G3P, which is used to build glucose and other organic molecules
Figure 7.10B
CALVINCYCLE
3
3 P
CO2
Step Carbon fixation. An enzymecalled rubisco combines CO2 with a five-carbon sugar called ribulose bisphosphate (abbreviated RuBP). The unstable product splits into two molecules of the three-carbon organic acid, 3-phosphoglyceric acid (3-PGA). For three CO2 entering, six 3-PGA result.
1 Input:In a reactioncatalyzed by rubisco,CO2 is added to RuBP.
P 6 PRuBP 3-PGA
1
G3P
6 P
2Step Reduction. Two che-mical reactions (indicated by the two blue arrows) consume energy from six molecules of ATP and oxidize six molecules of NADPH. Six molecules of 3-PGA are reduced, producing six molecules of the energy-rich three-carbon sugar, G3P
6 ATP
6 ADP + P
6 NADPH
6 NADP+
2
3Step Release of one molecule of G3P. Five of the G3Ps from step 2 remain in the cycle. The single molecule of G3P you see leaving the cycle is the net product of photosynthesis. A plant cell uses two G3P molecules to make one molecule of glucose.
Output: 1 PG3P
Glucoseand othercompounds
3
3
3 ADP
ATP
4Step Regeneration of RuBP. A series of chemical reactions uses energy from ATP to rearrange the atoms in the five G3P molecules (15 carbons total), forming three RuBP molecules (15 carbons).These can start another turn of the cycle.
5 P
G3P
4
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PHOTOSYNTHESIS REVIEWED AND EXTENDED7.11 Review: Photosynthesis uses light energy to make food molecules
Figure 7.11
Light
H2O CO2
NADP+
Photosystem II
Photosystem I
Electrontransport
chains
ADPP+
RUBP
CALVINCYCLE
(in stroma)3-PGA
Stroma
G3PNADPH
ATP
O2
LIGHT REACTIONS CALVIN CYCLE
Sugars
Cellular respiration
Cellulose
Starch
Other organiccompounds
Thylakoidmembranes
Chloroplast
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7.12 C4 and CAM plants have special adaptations that save water
• In C3 plants a drop in CO2 and rise in O2 when stomata close on hot dry days
– Divert the Calvin cycle to photorespiration
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• C4 plants first fix CO2 into a four-carbon compound
– That provides CO2 to the Calvin cycle
Figure 7.12 (left half)
Sugarcane
C4 plant
CALVINCYCLE
3-C sugar
CO2
4-C compound
CO2Mesophyll cell
Bundle-sheath cell
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• CAM plants open their stomata at night
– Making a four-carbon compound used as a CO2 source during the day
CO2
Figure 7.12 (right half) CAM plant
Day
CALVINCYCLE
3-C sugar
CO2
4-C compound
Night
Pineapple
CO2
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Discovery Video: Space Plants
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Boy, I’d like to jump out and go
swimming. Oh wait, I don’t like to
swim…Hmmm.
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THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY
7.6 Visible radiation drives the light reactions
• Certain wavelengths of visible light, absorbed by pigments
– Drive the light reactions of photosynthesis
Figure 7.6A, B
Increasing energy
10–5 nm 10–3 nm 1 nm 103 nm 106 nm 1 m 103 m
Gammarays
X-rays UV Infrared Micro-waves
Radiowaves
Visible light
400 500 600 700 750
650nm
Wavelength (nm)
Transmittedlight
Absorbedlight
Reflectedlight
Light
Chloroplast
380
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PHOTOSYNTHESIS, SOLAR RADIATION, AND EARTH’S ATMOSPHERE CONNECTION
7.13 Photosynthesis moderates global warming
• Greenhouses used to grow plants
– Trap solar radiation, raising the temperature inside
Figure 7.13A
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• Excess CO2 in the atmosphere
– Is contributing to global warming
Figure 7.13B
Sunlight
ATMOSPHERE
Some heatenergy escapesinto space
Radiant heattrapped by CO2
and other gases
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• Photosynthesis, which removes CO2 from the atmosphere
– Moderates this warming
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TALKING ABOUT SCIENCE
7.14 Mario Molina talks about Earth’s protective ozone layer
Figure 7.14A
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• Solar radiation converts O2 high in the atmosphere to ozone (O3)
– Which shields organisms on the Earth’s surface from the damaging UV radiation
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• Industrial chemicals called CFCs have caused dangerous thinning of the ozone layer
– But international restrictions on CFC use are allowing recovery
Figure 7.14B
Southern tip ofSouth America
Antarctica